1. Field of the Invention
The present invention relates to a wiring structure on a semiconductor substrate and, more particularly, to a wiring structure capable of preventing ion migration between interconnections formed at fine pitches, and a method of fabricating the same.
2. Description of the Related Art
A conventional semiconductor device called a CSP (chip size package) is as follows. On a semiconductor substrate having connecting pads on its upper surface, copper distribution wires are connected to the connecting pads via an insulating film interposed therebetween. A copper bump electrode is formed on a connecting pad portion of each distribution wire. An encapsulating film is formed on the insulating film and the distribution wires such that the upper surface of the encapsulating film is leveled with the upper surfaces of the bump electrodes (e.g., U.S. Pat. No. 6,600,234B2).
In the above conventional semiconductor device, as shown in FIG. 7 of U.S. Pat. No. 6,600,234B2, a wiring substrate metal layer is formed on a substantially flat upper surface of an insulating film. Therefore, if water in the use environment penetrates into the encapsulating film, copper ions flowing out from the wiring substrate metal layer or bum electrodes 57 to which a positive voltage is applied move in the interface between the insulating film and encapsulating film, and precipitate in the wiring substrate metal layer 56 or bump electrodes to which a negative voltage is applied, thereby causing a short circuit by so-called ion migration.
It is, therefore, an object of the present invention to provide a semiconductor device capable of preventing easy occurrence of a short circuit caused by so-called ion migration, and a method of fabricating the same.